He refused to celebrate, instead staring into the stands in the direction of the chants.

“Many players in the last month have suffered from racial abuse … I did yesterday to [sic],” Lukaku wrote on Instagram.

“Football is a game to be enjoyed by everyone and we shouldn’t accept any form of discrimination that will put our game in shame. I hope the football federations all over [the] world react strongly on all cases of discrimination.”

He also argued that social media platforms should take a stronger stance against racial abuse and added that “instead of going forward we’re going backwards … as players we need [to] unify and make a statement on this matter to keep this game clean and enjoyable for everyone.”

‘Identify, isolate and ban’

Inter boss Antonio Conte insists he did not hear the noises from his touchline position, but said in a news conference after the game that “in Italy we must improve a lot and be more educated and respectful towards those doing their job.”

“In other countries you support the team; you don’t insult the opposition like this,” Conte added. “There must be the maximum respect. Today I was treated well and wasn’t insulted, other times it hasn’t happened like that and it’s not nice.”

In a statement, Cagliari called Sunday’s incident “absolutely unacceptable” and affirmed the club’s intention “to identify, isolate and ban those ignorant individuals whose shameful actions and behaviors are completely against those values that Cagliari Calcio strongly promotes in all their initiatives.

It continued: “Full solidarity to Romelu Lukaku and even stronger commitment toward[s] annihilating one of the worst plagues that affects football and our world in general.

“However, as we are aware that technology is not enough, we believe our commitment needs real support by the rest of the football stakeholders: starting from all the true supporters, to all the stewards in the stands, from police and security agents, passing to media and as well through Lega Serie A and FIGC [the Italian FA].”

Muntari was booked after remonstrated with fans, after which he walked from the pitch and was booked again. He initially received a one-match ban that was later rescinded.

“It’s a club that has a history of repeat offenses in similar incidents,” Italian football journalist Adam Digby told CNN Sport.

“If you look at the way that these things are handled in England or in Germany, it just wouldn’t stand. It just carries on and on and on with Cagliari.

“The Italian FA’s refusal to condemn them for it — it remains to be seen if it will actually be given the official status that it has been a racist incident from a disciplinary point of view.”

In a broadcast of the game that was aired on ESPN, the commentator remarks on the abuse from fans after Lukaku scores the penalty. However, in the official highlights posted by Serie A, these remarks are edited out of the commentary.